Signaling by the mTOR protein kinase complex 1 (mTORC1) plays a major role in proper differentiation and development, and in regulating normal cellular homeostasis. When improperly regulated this signaling systems has been linked to a variety of diseases associated with altered metabolism such as aging, diabetes, obesity, immune disorders, neurodegeneration, diseased muscle physiology, benign tumor syndromes and malignant cancers. The overall goals of the previous funding period were to begin to define at a molecular and biochemical level how mTOR signaling controls cell growth through the regulation of protein synthesis, to initiate efforts to define the signaling landscape (the mTORC1 phospho-proteome) and biological processes regulated downstream of mTORC1, and to develop high-throughput, RNAi-based screens to extensively evaluate how mTORC1 is regulated by growth factors, oncogenes, tumor suppressors, nutrients, stress and cellular energy status. Our continuing success on all fronts has provided the foundation for the current proposal. From our innovative approaches and proposed research, we will illuminate previously unknown roles of C3G and various GEFs in mTORC1 activation (aim #1); define how and why AAs regulate the Ran gradient and the nuclear entry of Rags and/or mTORC1 (aim #2); and identify new molecular details of how mTORC1 regulates mRNA biogenesis (aim #3). Through these aims, we will identify and characterize new upstream regulators and downstream effectors of mTORC1, further explaining how improper regulation of mTORC1 contributes to a variety of human diseases. Furthermore, our research will result in the identification of new biomarkers and potential therapeutic targets needed for detection and intervention in human diseases resulting from improper mTOR signaling.